The invention relates to a method for lubricating the piston in the filling chamber of a diecasting machine.
In a diecasting machine, liquid metal is metered into the filling chamber, ejected from the filling chamber with the piston and injected into the mould cavity. During this process, the piston sliding on the hot cylindrical inner wall of the filling chamber and its piston rings are subjected to high stresses. Lubrication of the piston is therefore essential.
Pistons which are conventional nowadays consist of a Cu—Be alloy or of steel. Piston greases and oils as well as granules or pellets are used as lubricants. Graphite-free or graphite-containing oils are applied by drop or spray lubrication. With drop lubrication, the application takes place on the piston while it is located at the beginning of its stroke. With spray lubrication, the piston is also located at the beginning of its stroke and spraying takes place through the metal filling aperture, in other words ahead of the piston.
The lubricants which are conventional nowadays are based on mineral oil and are therefore not very environmentally friendly.
A method of the type mentioned at the outset is disclosed in U.S. Pat. No. 5,370,171.
The invention is based on a first object of developing a method of the type mentioned at the outset in such a way that a piston lubricant is optimally applied to the piston and the inner wall of the filling chamber.
A second object of the invention is the provision of an improved lubrication method with an environmentally compatible lubricant. The method should at least achieve the lubricating properties of the lubricant based on mineral oil.